1. Field of the Invention
This invention relates to an additive for well drilling fluids, to a process for preparing such an additive, and to the use of such an additive for the preparation of drilling fluids protected from loss of liquid.
2. Statement of Related Art
Deep well drilling industries use drilling fluids to convey tailings to the surface, to compensate the liquid or gas pressure of the formation, to cool the drill bit, to stabilize the geological formation and to reduce friction between the drilling pipe and the formation.
Two types of drilling fluids are basically distinguished, namely a water-based fluid and an oil-based fluid. As is already apparent from the name, the water-based fluid is a drilling fluid which contains water as the main component, the rheological/chemical properties of which are altered, in accordance with the requirements, by the addition of various additives.
In contrast thereto, the oil-based fluid contains diesel oil or so-called "clean oil" as the main component (apart from the weight-increasing material). This type of fluid is modified, analogous to water-based fluids, with rheology-changing additives which, however, due to the hydrophobic nature of the base component, are of a different chemical composition.
In recent years, oil-based drilling fluids have been used to an increasing extent: Today in oil fluids neat oil is not used as the liquid phase, but rather a water-in-oil emulsion, the oil being the continuous phase.
Such inverse emulsions mostly have an oil/water ratio of about 80/20, although they may be employed at an oil/water ratio of 60/40.
Which fluid type is employed will depend not only on the chemical, thermal and mechanical peculiarities of the respective drill hole, but will also be determined by ecological and other aspects.
There are a variety of additives which may be added to both types of fluids in order to determine the properties thereof. One such additive is a "fluid loss additive". This is an additive which prevents the fluid from streaming into the often porous formation under the action of temperature and pressure.
Such a loss in fluid not only involves financial drawbacks because of the lost drilling fluid, but may also deteriorate the total stability of the drilling hole by washing out the formation, loss in back pressure, and the like, and thus adversely affect the environment.
Numerous humic acid derivatives have been disclosed as suitable for use as a fluid loss additive.
U.S. Pat. No. 3,168,475 (and corresponding German published patent application 11 81 707) disclose a process for the preparation of humate salts with substituted amines, wherein lignite is digested with an alkaline aqueous solution and, after neutralization, is reacted with an ammonium salt in aqueous solution.
German published patent application 12 49 788, also corresponding to U.S. Pat. No. 3,168,475, relates to a process for the treatment of an oil-containing drilling fluid wherein the latter, in order to avoid excessive oil losses, is admixed with a humate which is a salt of humic acid with higher amines.
European published patent application 49,484 discloses a process for the preparation of an additive for reducing fluid losses for oil-based drill hole working fluids. The additive is prepared by mixing brown (lignite) coal or humic acid with an oil-soluble or oil-dispersible amine salt, amide-amine or amide-amine salt.
Further amine and amide derivatives have been disclosed in the U.S. Pat. Nos. 3,281,458; 3,755,447; 3,671,427; 4,597,878; and 3,494,865.
U.S. Pat. No. 4,421,655 discloses a fluid loss additive consisting of a polyphenol compound which may be humic acid, certain ammonium compounds and a polyvalent metallic cation. The cation may be calcium, magnesium, iron, zinc, nickel, chromium or aluminum; calcium being preferred.
The various known additives are generally prepared by heating in the presence of a solvent.
German patent application 37 11 959.8, is commonly assigned, and although mentioned in the German priority document to the present disclosure is unpublished as of the filing date of the present disclosure and therefore is not prior art. It describes an additive to drilling fluids containing an organometal compound having the general formula: EQU L.sub.x M(OR).sub.y X.sub.z
wherein
M is titanium, zirconium or vanadium,
L is a humic acid moiety,
R is C.sub.1-6 alkyl, and preferably C.sub.3 - or C.sub.4 -alkyl,
X is a long-chain fatty acid residue OOCR'; a long-chain aliphatic or aromatic sulfonic acid residue --SO.sub.3 R"; a long-chain alcohol residue --OR'; a long-chain amidoamine residue R"'NCOR'; or a long-chain amine residue --NR'R'; wherein R' is C.sub.10-22 (preferably C.sub.14-18) alkyl or alkenyl, R" is aryl or R', and
R"' is H or a C.sub.1-22 (preferably C.sub.1-18) alpihatic and
x is 1, 2, 3 or 4,
z is 1, 2, 3 or 4,
y v-x-z, v being the valence of M, wherein no inorganic carrier for the additive is present, as well as its preparation and its use as a "fluid loss agent."